In general, a number of insulative tools have been devised and are commercially available for use in performance of work on equipment and componentry that are energized at high electrical voltages. Their individual designs, for example in respect of their composition, structural designs and dimensions, are tailored to accommodate the safe handling of equipment and componentry energized to different levels. The basic principles governing such design requisites for the different types of insulative tools are generally known in the art, and overall guidelines and specifications are available for insulative tool manufacturers and users to ensure, in part, the minimal approach distance or separation between the energized equipment/componentry and the worker.
For example, one type of insulative tools commonly used for work on high-voltage electricity equipment or componentry is an elongated insulative pole with different adaptors and tools affixed onto a terminus thereof for performing different tasks and functions. A basic insulative pole is made of simple insulative materials such as plastic and is reinforced with fibreglass. Typical simple one-piece insulative poles that are available commercially are substantially cylindrical in configuration with lengths varying from approximately 6 feet to over 14 feet and cross sectional diameters (perpendicular to the longitudinal direction of the tool) varying from approximately 1 inch to 2 inches. More recent advances in insulative pole design include telescopic versions of insulative poles as described in U.S. Pat. No. 4,079,978 and U.S. Pat. No. 5,593,196.
With reference to above, the assortment of insulative poles is designed specifically for work on equipment or componentry energized to different levels. As a general rule of thumb, higher levels of energization require the use of insulative poles with greater lengths so to provide a safe distance between the worker and the energized equipment or componentry. For reference, a comprehensive listing of said minimum lengths of insulative poles relative to different levels of energization of the equipment or componentry (minimum approach distances) can be found in 29 CFR 1926.950-OSHA (American Society for Testing and Materials (ASTM) specifications), the Institute of Electrical and Electronic Engineers (IEEE) Standard 516-1995, and the Intenational Electrotechnical Commission (IEC) Standard 61472.
In additional to the inherent designs of insulative tools, it is also known that imperfections, damage, contamination and/or moisture on the surface of insulative tools can individually and/or collectively impact upon the insulative properties and reduce the safety of insulative tools. In essence, the presence of any, or a combination, of the aforementioned conditions reduces the inception voltage for dangerous electrical discharges, and correspondingly, stringent government regulated specifications and guidelines are in place to govern routine maintenance and inspection of high voltage insulative tools so to safeguard against arcing accidents.
Nevertheless, despite the most current designs and the industry's diligent use of conventional measures to maximize safety of insulative tools and safeguarding workers, occurrence of electrical discharges and arcing accidents from work on high voltage equipment and componentry remains a reality often resulting in severe injury to the workers involved, and at times, mortality.
A number of devices have been developed and taught in the prior art to enhance the safety of insulative tools.
One category of devices consists of mechanical attachments to a terminus of an insulative pole solely to improve functional dexterity in manipulation of energized equipment or componentry and reduce the likelihood of accidents due to mishandling of the energized equipment or componentry. A variety of connectors and tools of varying complexity has been taught in the prior art, for example, U.S. Pat. No. 3,624,592 teaches an inverted V-shaped hook that is adaptable to a terminus of an insulative pole; U.S. Pat. No. 3,866,965 teaches another attachment with radially projecting arms; U.S. Pat. No. 3,868,136 teaches an interior insulating rod coaxially and slidably within a hollow tubular insulating pole; U.S. Pat. No. 4,326,316 teaches a rotary brush device, again attachable to a terminus of an insulative pole, for cleaning aerial conductors; U.S. Pat. No. 4,965,930 teaches a set of pivoting jaws and a hook mountable onto a terminus of an insulative pole; U.S. Pat. No. 5,299,464 teaches a selective transformer penetration tool adaptable onto an insulative pole for remote sampling of oil from high voltage transformers; U.S. Pat. No. 5,564,852 teaches an adaptor connecting a tool to a terminus of an insulative tool which comprises of two members movable relative to each other to improve the adjustability and flexibility of tool angle with respect to the insulative pole; and U.S. Pat. No. 6,332,368 teaches a sampling tool mountable to a terminus of an insulative pole for sampling of aerial electrical equipment and componentry.
Another category of devices that has been developed to improve the safety of insulative poles consists in general of shields that can be affixed to an insulative pole so to act as a literal physical barrier between the worker and the energized equipment or componentry. For example, U.S. Pat. No. 5,077,448 teaches a transparent plastic protection shield that can be singly and releasably attached to an insulative pole in a manner that the shield is located close to the terminus of said insulative pole that is in contact with or near the energized equipment or componentry. In accordance to the inventor, positioning of the shield close to the equipment or componentry best protects a worker, who would be situated at the other terminus of the insulative pole, from any spent or disintegrated electrical parts or debris dislodged or ejected away from the energized equipment or componentry. U.S. Pat. No. 5,666,253 also describes a single protective shield attached to an insulative pole to provide physical barrier between the worker and the energized equipment in which the shield is made of a transparent and impact-resistant thermoplastic material with an opening formed in the shield plate for receiving an insulative pole therethrough. U.S. Pat. No. 4,230,357 also teaches a single physical shield circumferentially affixed to an insulative pole, in this instance a downwardly opening frustoconical flexible guard made of an insulative, nonconductive material, is fitted around the insulative pole solely to cover the worker's hand and to restrict movement of a worker's hand near the energized equipment or componentry.
As evident from the aforementioned references, safety devices of the prior art have all been developed to provide simple physical aids and simple physical barriers or shields to protect the worker from accidentally becoming in contact with the energized equipment or componentry or from debris ejected from the energized equipment or componentry towards the worker. None of the above provides any solution or means to protect the worker from the electrical fields that transcend the length of an insulative pole so to prevent dangerous electrical discharges that may be associated or result from said electric fields.
It is therefore the primary objective of the present invention to provide a novel category of safety devices to further improve upon the safety of insulative tools and to protect the worker from ill-effects associated with the electrical fields transcending along insulative tools or poles when in contact with or near energized equipment or componentry.
It should be readily apparent to a person skilled in the art that the safety devices of the present invention may be used singly or used in combination with any of the aforementioned safety devices of the prior art that are oriented towards physical protection of the worker.